C. F. Keil and Franz Delitzsch on 2 Chronicles 11:21-22

2Ch 11:21-22

Only these wives with their children are mentioned by name, though besides these Rehoboam had a number of wives, 18 wives and 60 (according to Josephus, 30) concubines, who bore him twenty-eight sons and sixty daughters. Rehoboam trod in his father’s footsteps in this not quite praise-worthy point. The eldest son of Maachah he made head (לראשׁ), i.e., prince, among his brethren; להמליכו כּי, for to make him king, scil. was his intention. The infin. with ל is here used in the swiftness of speech in loose connection to state with what further purpose he had appointed him נגיד; cf. Ew. §351, c, at the end.